Ogre Lexicon  »  -Billboard

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Billboard - A flat square polygon (2 triangles) for high speed displaying of 2D textures. Mostly the face points to the camera. Often it's also called sprite, although this not right in historical context (see Wikipedia article and sprites on C64).

To make one, you first have to make a BillboardSet. Then, the billboards can be added to it on a given position. The BillboardSet is a MovableObject and should therefore be added to a SceneNode.

Billboards can be used e.g. to create a HUD (heads up display) for characters.

Types of Billboard:

• BBT_POINT:
  Standard point billboard (default), always faces the camera completely and is always upright

• BBT_ORIENTED_COMMON:
  Billboards are oriented around a shared direction vector (used as Y axis) and only rotate around this to face the camera

• BBT_ORIENTED_SELF:
  Billboards are oriented around their own direction vector (their own Y axis) and only rotate around this to face the camera

• BBT_PERPENDICULAR_COMMON:
  Billboards are perpendicular to a shared direction vector (used as Z axis, the facing direction) and X, Y axis are determined by a shared up-vertor

• BBT_PERPENDICULAR_SELF:
  Billboards are perpendicular to their own direction vector (their own Z axis, the facing direction) and X, Y axis are determined by a shared up-vertor

Example

On right side is an example usage (from the Ogre game APOX).

A billboard used for a green circle marker. The face doesn't point to the camera - the billboard is parallel to the terrain. It's not rendered on top (behind the helicopter model). For this the RenderQueue was modified and maybe some material settings were changed (Depth Check ON/OFF, Depth Write ON/OFF, etc.). The usage of billboards supports high performance. An alternative would be to use Projective Decals which renders an additional layer to a texture. (But this would be slower, when you need to update its size/position for each frame.)

See Also   Example how to add to a scene MOGRE MovableText by Billboards - shows text, clamped to a SceneNode Example for Mogre Billboards, Materials and Lights Billboard Class Reference in API BillboardSet Class Reference in API SpriteManager2d | MOGRE SpriteManager2d - code snippet An advanced description is in the book Pro OGRE 3D Programming (ISBN 1-59059-710-9) OgreSprites - similar, but without use of Billboard MovableText | MOGRE MovableText | MovableTextOverlay - similar, but only for text ManualObject 2D Overlay 2.5D graphics at Wikipedia Billboarding (Direct3D 9) at MSDN Projective Decals - render an additional texture layer to a 3D model ObjectTextDisplay - Displaying 3D Object Text in 2D Without Using Billboards

 
See also: Sprite (computer graphics) (Wikipedia)